CD44 and X-linked hydrocephalus with stenosis of the aqueduct of Sylvius: On the basis of a previous Col4a5-deficient mouse model that mimics clinical XLAS renal symptoms (Wu et al. 2023), we discovered notable upregulation of CD44 and TGFβ, together with substantial accumulation of HA in the renal tissues of Col4a5 mutant mice compared with those of healthy controls.